<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            margin: 0;
            padding: 0;
            /* box-sizing: border-box; */
        }

        .container {
            height: 450px;
            display: flex;
        }

        .left {

            height: 100%;
            background-color: rgb(136, 206, 235);
            flex: 1;
            border-right: 10px solid white;
        }

        .right {
            display: flex;
            flex: 4;
            height: 100%;
            flex-wrap: wrap;
        }

        .right .item {
            width: 25%;
            height: 50%;
            background-color: rgb(255, 166, 0);

            border-right: 10px solid white;
            border-bottom: 10px solid white;
            box-sizing: border-box;
        }

        .right .item:nth-child(4n) {
            border-right: 10px solid red;
        }

        .right .item:nth-child(n+5) {
            border-bottom: 10px solid green;
        }
    </style>
</head>

<body>
    <div class="container">
        <div class="left"></div>
        <div class="right">
            <div class="item"></div>
            <div class="item"></div>
            <div class="item"></div>
            <div class="item"></div>
            <div class="item"></div>
            <div class="item"></div>
            <div class="item"></div>
            <div class="item"></div>
        </div>
    </div>
</body>

</html>